Immersion lithography is emerging as a technology for extending optical photolithography to smaller image sizes than currently printable with conventional optical lithography tools. Immersion lithography tools place an immersion liquid in direct contact with the photoresist layer to be exposed and the final image-focusing lens of the immersion lithography system is either immersed in the liquid or placed in very close proximity to the immersion liquid. The immersion liquid allows an increase of the capture angle of the Raleigh criterion of resolution (thus increasing resolution) by application of Snell's law of refraction and thus smaller images can be formed than could otherwise be possible in lithography systems with only air between the photoresist layer and the final image-focusing lens.
However, a significant problem with immersion lithography is the creation of contaminant residues on the photoresist surface and on the surface of the semiconductor substrate in regions where the photoresist is subsequently developed away. These residues can cause physical yield and reliability defects as well as degradation of electrical parameters of the integrated circuit devices being fabricated.
Therefore, there is a need for a method and apparatus for preventing or reducing formation of contaminant residues and for removing contaminant residues formed during immersion lithography.